The present invention relates to the field of data compression and in particular, discloses an architecture for decoding coefficients that, have been constructed as a result of a compression process. The invention also relates to a computer program product, including a computer readable medium having recorded thereon a computer program for decoding a bitstream of previously encoded coefficients.
The field of digital data compression and in particular digital image compression has attracted great interest for some time.
In the field of digital image compression, many different techniques have been utilized. In particular, one popular technique is the JPEG standard, which utilizes the discrete cosine transform to transform standard size blocks of an image into corresponding cosine components. In this respect, the higher frequency cosine components are heavily quantised so as to assist in obtaining substantial compression factors. The heavy quantisation is an example of a xe2x80x9clossyxe2x80x9d technique of image compression. The JPEG standard also provides for the subsequent lossless compression of the transformed coefficients.
Recently, the field of wavelet transforms has gained great attention as an alternative form of data compression. The wavelet transform has been found to be highly suitable in representing data having discontinuities such as sharp edges. Such discontinuities are often present in image data or the like.
Although the preferred embodiments of the present invention will be described with reference to the compression of image data, it will be readily evident that the preferred embodiment is not limited thereto. For examples of the many different applications of Wavelet analysis to signals, reference is made to a survey article entitled xe2x80x9cWavelet Analysisxe2x80x9d by Bruce et. al. appearing in IEEE Spectrum, October 1996 pages 26-35. For a discussion of the different applications of wavelets in computer graphics, reference is made to xe2x80x9cWavelets for Computer Graphicsxe2x80x9d, I. Stollinitz et. al. published 1996 by Morgan Kaufmann Publishers, Inc.
It would be desirable to provide for a form of hardware embodiment of a decoder so as to provide for efficient and effective decoding of a series of wavelet coefficients previously encoded in order to substantially increase the speed of decoding.
It is an object of the present invention to ameliorate one or more disadvantages of the prior art.
According to one aspect of the invention there is provided an apparatus for decoding a stream of previously encoded coefficients including:
input means for receiving said stream of encoded coefficients;
bit plane level monitoring means connected to said input means and adapted to monitor a current bit plane level from said stream of coefficients;
pixel generation means interconnected to said input means and said bit plane level monitoring means and adapted to utilize said current bit plane level for generating output coefficient values each having a predetermined size.
According to another aspect of the invention there is provided a method of decoding a bitstream of previously encoded coefficients, the method including the following steps:
(i) inputting the bitstream of encoded coefficients;
(ii) determining a current bitplane level of bits within said stream; and
(iii) generating output coefficient values each having a predetermined number of bits utilizing said current bitplane level and bit fragments within said bitstream. According to another aspect of the invention there is provided an apparatus for decoding a bitstream of previously encoded coefficients, the apparatus including: input means for inputting the bitstream of encoded coefficients;
determination means for determining a current bitplane level of bits within said stream; and
generation means for generating output coefficient values each having a predetermined number of bits utilizing said current bitplane level and bit fragments within said bitstream.
According to another aspect of the invention there is provided a computer program product including a computer readable medium having recorded thereon a computer program for decoding a bitstream of previously encoded coefficients, the computer program product including:
input means for inputting the bitstream of encoded coefficients;
determination means for determining a current bitplane level of bits within said stream; and
generation means for generating output coefficient values each having a predetermined number of bits utilizing said current bitplane level and bit fragments within said bitstream.